The technique of early harvesting including field shelling and subsequent conditioning of corn and other cereal grains in storage is becoming increasingly popular. The present methods of conditioning of drying these cereal grains range from simply storing the seeds and letting them dry in the atmosphere to placing them in drying bins and passing heated air through the grain seeds. In more recent years, complicated mechanical devices for agitating the stored grain or removing the bottom-most layer of stored grain have increased equipment and operational expenses and severely damaged both the physical and food properties of the grains and not infrequently the storage structure itself.
Grain exposed by storing in atmospheric air frequently is inadequately dried, and in most cases the drying process is so slow that problems of mold and biochemical changes result in serious losses to the stored grain. Also, drying of this type is interrupted by undesirable weather conditions, such as high humidity or prolonged wet and rainy periods, both of which result in accelerated degradation of the stored grain.
Wet grain that is artificially dried by flow of heated air in a drying bin is frequently damaged due to the fact that commercial drying techniques often use drying air temperatures of from 100.degree. F. to 140.degree. F., and sometimes even as high as 200.degree. F., with resultant destruction of enzymes and amino acid proteins and other volatile ingredients.
The early harvesting techniques used in producing corn today frequently involve field shelling of the corn when it is at about 27% moisture. At this moisture level grain deteriorates rapidly and becomes mold infested. Corn approaches physiological maturity when its moisture content is approximately 20%. The maturing process involves not only the removal of moisture, but also chemical stabilization. Because mature corn is more stable it may be stored safely over long periods under proper conditions, while storing of corn with excessive moisture prevents the natural occurrence of biological maturity. Maturing involves the chemical stabilization of starch and protein which constitutes about 85% of the corn kernel. In the maturing process, sugar molecules bond together to form starch molecules which are more complex carbohydrates and are more stable chemically. Similar processes are involved with proteins and amino acids. In these processes water is eliminated, and thus drying or the elimination of water is an essential aspect of maturing of grain. Temperature and moisture are both factors in grain stabilization; however, above certain moisture levels, chilling of grain does not prevent deterioration of the seed.
______________________________________ GERMINATION LOSS IN STORED, REFRIGERATED CORN. GERMINATION EMERGENCE* AFTER AFTER AFTER AFTER MOISTURE 6 MOS. 18 MOS. 6 MOS. 18 MOS. ______________________________________ Above 24% 17% 0% 0% 0% 18-24% 42% 13% 33% 53% 16-18% 74% 71% 59% 88% 14-16% 70% 73% 56% 86% 12-14% 75% 75% 47% 93% 10-12% 65% 69% 70% 91% Under 10% 74% 73% 75% 84% AVERAGE 56.5% 82.5% ______________________________________ Storage temperature approximately 35.degree. F. *Percentage Emergency within five days of planting.
A comprehensive discussion of synthesis and hydrolysis of starch and protein in grain may be found in U.S. Pat. No. 3,408,747, which also discloses a process of conditioning grain which relies on specific volumes of air flow through the grain to be dried.